Looking for aggregate census data and boundary files?  Check out the National Historical Geographic Information System.  They include census information from 1790 to the present.

Through the NHGIS Data Finder, users may:

• Filter and sort through thousands of available tables and boundary files
• Select and download multiple tables and boundary files, for different geographic levels and from different years, all in one request

All free of charge!

They have currently released:

• 2013 American Community Survey 1- and 3-Year Summary Files
• 2012 American Community Survey 1-, 3-, and 5-Year Summary Files and associated GIS boundary files
• 2009 American Community Survey 5-Year Summary Files and associated GIS boundary files
• Time Series Release 5: 17 new tables including Poverty Status, Ratio of Income to Poverty Level, Means of Transportation to Work, and Households by Household Type
• Data Finder improvements for a better user experience

NHGIS is also preparing the 2013 ACS 5-year Summary Files and 2013 GIS boundary files for release by early 2015.